The Inside Form is one of the most-used jigs you will have in your shop. The Inside Form if very popular with many luthiers for many reasons, which we will discuss below. Inside Forms can be used for most any acoustic instrument including acoustic and classical guitars, ukuleles, mandolins and hollow body electrics.
What Are The Alternatives?
Side Forms: There are alternatives to using the inside form that are shown on the Georgia Luthier Supply shopping site, and
they are very good alternatives. One of the options is to use a Side Form. These forms are made from 3 layers of cabinet grade 19mm plywood. They are hinged at the top and have an adjustable toggle clamp at the bottom. These forms are very popular with luthiers as they are relative inexpensive, lightweight, easy to use and easy to make. We offer these forms pre-built for any acoustic instrument that we carry. If you have a custom size instrument you would like us to build for you, let us know and we can work up a quote for you.
Adjustable Inside Form: These are a highbred tool and allow for a lot of versatility. These forms are completely adjustable in that the Adjustable Guitar Inside Form can securely hold any acoustic or classical guitar shape we offer. The Ukulele Adjustable Inside Form will work for all sizes of ukuleles we offer. These forms are great tools for a multitude of luthier operations from holding sides in position after bending to the installation of top and back plates and binding and purfling installations.
Reducing Stress in Side Wood:
I’m not saying that with an Inside Form you can be less attentive to the Spring-Back issues or worry less about the guitar being a bit “out of shape”. What the Inside Form allows you to do is to take the sides fresh from the Side Bending Jig and place them in an environment that allow them to fully cure in the proper shape. If there is some amount of spring-back (and there almost always is), visit the article on Solving Side Spring-Back for many different alternatives for you to consider on addressing this issue.
Do You Need Several Different Forms?
First of all you will need a different Guitar Inside Form for each shape guitar you intend to make. Actually the Classical Guitar Inside Form is quite different from the Acoustic Guitar Inside Form in that the Form for the Classical Guitar has to allow for the neck to be fastened to the sides at a very early stage because of the manner in which the sides are slipped into the neck and foot.
With the Acoustic Guitar and Ukuleles, on the other hand, you can nearly complete the body of the instrument before the neck is attached. Therefore provisions are necessary on the form for the Classical to allow the neck to stick through. This is done by means of a removable “gate”.
Inside Form Uses:
Correcting Side Spring-Back
Gluing the Head and Tail Blocks
Glue Lining on the Sides
Gluing the Top to the Sides
Gluing the Back to the Sides
Routing and Installing all Purfling and Bindings
There are many additional uses – almost too many to mention, for this invaluable guitar workshop jig.